This is not an STunnel issue but an OpenSSL libraries/defaults issue.
In Ubuntu 22.04 and later with the last set of major OpenSSL changes applied, the OpenSSL defaults for supported ciphers and protocols has changed. As such, TLS 1.0 is considered bad for use and the defaults in OpenSSL deny use of them.
This will require you to revise system-wide settings to allow TLS 1.0 or explicitly enabling TLS 1.0 in your stunnel configs.
-------- Original message --------
From: Stefano Pelli <ste.pelli@tiscali.it>
Date: 10/23/23 07:47 (GMT-05:00)
To: stunnel-users@stunnel.org
Subject: [stunnel-users] TLSV1.0